Information transmission device, system, and method

ABSTRACT

A network includes nodes that transmit information to each other. Some nodes operate intermittently; other nodes operate continuously. Information is transmitted to an intermittently operating node by a handshaking protocol in which the intermittently operating node indicates that it is ready to receive. Information is transmitted to a continuously operating node without such handshaking, thereby saving time and power. Each transmitting node has a memory storing information indicating which other nodes require handshaking.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 12/230,125,filed on Aug. 25, 2008. Furthermore, this application claims the benefitof priority of Japanese application 2007-227376, filed Sep. 3, 2007. Thedisclosures of these prior U.S. and Japanese applications areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an information transmission device,system, and method in which handshaking is used for power-savingpurposes.

2. Description of the Related Art

Sensor networks and other networks that transmit information ofteninclude battery-driven nodes that operate only intermittently and powerdown or ‘sleep’ when not operating, in order to extend their batterylife. Since a node cannot receive transmitted information while asleep,the transmitting node must use some scheme to make sure that thereceiving node is ready. One such scheme is the RICER (ReceiverInitiated CyclEd Receiver) handshaking scheme proposed by Lin et al. in‘Power-Efficient Rendez-vous Schemes for Dense Wireless Sensor Networks’in the proceedings of the IEEE International Conference onCommunications, pp. 3769-3776, 2004, in which a node with information totransmit waits to receive a signal indicating that the destination nodeis awake before beginning the transmission. The RICER scheme will befurther described in the detailed description of the invention.

Actual networks (multi-hop networks, for example) often include bothbattery-powered nodes, transmission to which requires this type ofhandshaking, and externally powered nodes, transmission to which doesnot require such handshaking. A problem with use of the RICER scheme inthese networks is that the RICER scheme always employs handshaking. Evenin a transmission to a node that is always awake, extra signals mustfirst be transmitted and received to confirm that the node is awake.This consumes extra power and delays the information transmissionprocess.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an informationtransmitting device, system, and method that can transmit informationwith handshaking when such handshaking is necessary, and can transmitinformation without handshaking when handshaking is unnecessary.

The invention provides an information transmitting device fortransmitting information to one or more destination devices. Theinformation transmitting device is operable in a plurality oftransmission modes, including at least a power-saving transmission modethat includes the transmitting and receiving of power-saving handshakingsignals and a normal transmission mode that excludes the transmittingand receiving of the power-saving handshaking signals.

The information transmitting device has a memory for storing informationindicating whether or not each destination device requires power-savinghandshaking, and a control unit that selects the power-savingtransmission mode or the normal transmission mode according to theinformation stored in the memory.

The destination devices may periodically transmit signals indicatingwhether or not they require power-saving handshaking. A destination nodethat requires power-saving handshaking may transmit these signals aspower-saving handshaking signals.

The invention also provides a network of nodes, including at least onenode that operates as a destination node requiring power-savinghandshaking, another node that operates as a destination node notrequiring power-saving handshaking, and another node that operates as aninformation transmitting device as described above.

By avoiding the unnecessary transmission and reception of power-savinghandshaking signals, the invention avoids needless transmission delaysand saves power, thereby extending the battery life of battery-powerednodes.

BRIEF DESCRIPTION OF THE DRAWINGS

In the attached drawings:

FIG. 1 is a state transition diagram of a conventional transmittingnode;

FIG. 2 is a state transition diagram of a conventional receiving node;

FIG. 3 illustrates a conventional transmission sequence;

FIG. 4 is a block diagram illustrating a transmitting node in a firstembodiment of the invention;

FIG. 5 is a state transition diagram of the transmitting node in FIG. 4;

FIG. 6 a block diagram illustrating a receiving node in a secondembodiment of the invention;

FIG. 7 is a state transition diagram of the receiving node in FIG. 6;and

FIG. 8 is a block diagram illustrating an information transmittingsystem with multiple nodes.

DETAILED DESCRIPTION OF THE INVENTION

A more detailed description of the conventional RICER scheme and twoembodiments of the present invention will now be given with reference tothe attached drawings, in which like elements are indicated by likereference characters. For brevity, information will sometimes bereferred to as data.

The following descriptions pertain to a communication system such as amulti-hop network with a plurality of information transmitting devicesor nodes that transmit information to each other. The network includesat least one power-saving node such as a battery-powered node thatoperates intermittently and requires power-saving handshaking to receivetransmitted information, and at least one non-power-saving node such asan externally powered node that operates continuously and does notrequire power-saving handshaking in order to receive transmittedinformation.

According to the conventional RICER scheme, all nodes transmit andreceive information according to protocols illustrated by the statetransition diagrams in FIGS. 1 and 2 and the communication sequencediagram in FIG. 3.

At the top of FIG. 3, the receiving node is in the sleep state, which isstate S201 in FIG. 2. At regular intervals, a timer in the receivingnode times out and the receiving node makes a transition S202 to theready-to-receive state S203.

In the ready-to-receive state S203, the receiving node sends aready-to-receive signal S301 and waits for a predetermined time toreceive an acknowledging signal or ACK signal S302. If an ACK signalS302 is received within the predetermined time, the receiving node makesa transition S204 to the information receiving state S205 and receivesinformation transmitted by the transmitting node. At the end of theinformation transmission, the receiving node makes a transition S206back to the sleep state S201.

If no ACK signal S302 is received within the predetermined time in theready-to-receive state S203, the receiving node makes a transition S207directly to the sleep state S201.

At the top of FIG. 3, the transmitting node is in an information waitingstate, which is state S101 in FIG. 1. The transmitting node has noinformation or data to transmit to the receiving node, so it does notrespond to the ready-to-receive S301 signal transmitted by the receivingnode. When an event produces information to transmit, the transmittingnode makes a transition S102 to the ready-signal waiting state S103, andwaits to receive another ready-to-receive signal from the receivingnode. When the next ready-to-receive signal S301 is received, thetransmitting node makes a transition S104 to the acknowledging (ACK)signal sending state S105, and acknowledges the ready-to-receive signalby transmitting an acknowledging signal S302 to the receiving node. Atthe end of transmission of the acknowledging signal, the transmittingnode makes a transition S106 to the information transmitting state S107,and transmits information (data) S303 to the receiving node. At the endof the information transmission, the transmitting node makes atransition S108 to the waiting state S101 to await the occurrence ofmore information to transmit.

If the receiving node is a non-power-saving node, the sleep state S201in FIG. 2 is eliminated. In the ready-to-receive state S203, anon-power-saving node transmits ready-to-receive signals S301 at regularand frequent intervals. After receiving an acknowledging signal and thefollowing information, the non-power-saving node returns from theinformation receiving state S205 to the ready-to-receive state S203.

The frequent transmission of ready-to-receive signals by anon-power-saving node wastes power. A more serious problem is that totransmit information to a non-power-saving node, a battery-operatedpower-saving node must waste time while waiting for a ready-to-receivesignal, expend power by remaining awake during this wasted time, thenwaste further time and power by transmitting an acknowledging signal.

First Embodiment

Referring to FIG. 4, the first node embodying the present invention is atransmitting node 400 comprising at least a data communication unit 401,a communication control unit 402, and a memory 403.

The data communication unit 401 performs information communicationfunctions under the control of the communication control unit 402, towhich the data communication unit 401 is connected.

The communication control unit 402 is connected to the datacommunication unit 401 and the memory 403, and controls communication byselecting different communication modes. One selectable mode is apower-saving transmission mode in which transmission starts afterreception of a predetermined signal from the destination node. Anotherselectable mode is a normal transmission mode in which transmission canstart at any time. The communication control unit 402 selects thepower-saving transmission mode or the normal transmission mode accordingto information stored in the memory 403.

The memory 403 has prestored information identifying destination nodesfor which power-saving transmission control is unnecessary, and providesthis information to the communication control unit 402, to which thememory 403 is connected. The information stored in the memory 403 may beinput by a user or obtained from a server or other external source, suchas another node in the communication system.

The operation of the first embodiment will now be described withreference to FIG. 5, which indicates state transitions of thetransmitting node in FIG. 4. The description will focus on thedifferences from the conventional operation shown in FIG. 1.

When an event produces data to transmit to a destination node, thecommunication control unit 402 of the transmitting node 400 makes atransition (S102) to a decision state (S501) to decide if power-savinghandshaking is necessary or not. The decision is based on theinformation stored in the memory 403.

If there is stored information in the memory 403 identifying thedestination node as a node that does not require power-savinghandshaking, that is, as a non-power-saving node, the communicationcontrol unit 402 selects the normal transmission mode and makes animmediate transition (S502) to the data transmitting state (S107).Transmission of data to a non-power-saving node can therefore beperformed without waiting for a ready-to-receive signal.

If there is no information stored in the memory 403 identifying thedestination node as a non-power-saving node, the communication controlunit 402 selects the power-saving transmission mode and makes atransition (S503) to the ready-signal waiting state (S103). When aready-to-receive signal is received (S104), an acknowledging (ACK)signal is transmitted (S105). After completion of the transmission ofthe acknowledging signal (S106), the data are transmitted (S107).Communication with a power-saving node is thus performed withpower-saving handshaking as in the prior art.

As described above, in the first embodiment, the transmitting node usesthe power-saving mode and normal mode selectively, based on storedinformation identifying non-power-saving nodes. Communication with anon-power-saving node can therefore take place without unnecessaryhandshaking. This has the following advantages.

First, when the receiving node is a non-power-saving node, thetransmitting node can transmit data with less expenditure of power,because it does not have to transmit and receive handshaking signals.

Second, when the receiving node is a non-power-saving node, thetransmitting node can transmit data without waiting for aready-to-receive signal, resulting in less transmission delay.

Although the first embodiment is based on a receiver-initiated system inwhich power-saving handshaking is initiated by the destination node (bytransmission of the ready-to-receive signal), the invention is alsoapplicable in systems in which power-saving handshaking is initiated bythe transmitting node, as in the TICER (Transmitter Initiated CyclEdReceiver) scheme described by Lin et al. The transmitting node storesinformation identifying nodes that do not require power-savinghandshaking, and skips the power-saving handshaking procedure intransmissions to these nodes. The same two advantages are obtained.

The communication modes are not limited to a single power-savingtransmission mode and a single normal transmission mode. There may bemore modes. For example, both transmitter-initiated andreceiver-initiated power-saving handshaking modes may be available, andthe memory may also store information for choosing between thesedifferent power-saving transmission modes.

Second Embodiment

In the second embodiment, the information identifying nodes notrequiring power-saving handshaking is not prestored in the memory of thetransmitting node but is acquired in the course of communication. Areceiving node that operates continuously sends information to thetransmitting node indicating that power-saving handshaking is notrequired, and the transmitting node updates its memory contentsaccording to this information.

The node in the block diagram in FIG. 6 is a non-power-saving receivingnode 600 that communicates with the transmitting node 400 described inthe first embodiment. The receiving node 600 comprises a datacommunication unit 601 and a communication control unit 602.

The data communication unit 601 performs information communicationfunctions under the control of the communication control unit 602, towhich the data communication unit 601 is connected.

The communication control unit 602, controls data receiving operationsand causes the data communication unit 601 to transmit information tosurrounding nodes indicating that that no power-saving handshaking isnecessary for transmission to the receiving node 600.

The operation of the second embodiment will be described with referenceto FIG. 7, which illustrates state transitions of the receiving node inFIG. 6. The description will focus on the differences from theconventional operation illustrated FIG. 2.

The receiving node 600 operates continuously; it does not periodicallyenter a sleep mode. Normally, the receiving node 600 is in thedata-receiving state (S205), which now includes the ready-to-receivestate. If the receiving node 600 receives an acknowledging (ACK) signal(S204), it simply remains in the data-receiving state (S205).

At regular intervals, however, a timer in the receiving node times outand the receiving node makes a transition (S701) to a transmitting state(S702) in which the communication control unit 602 causes the datacommunication unit 601 to transmit a signal to the surrounding nodesinforming them that the receiving node 600 does not require power-savinghandshaking. A multi-address transmission mode is employed. Aftertransmitting this signal, the receiving node 600 makes a transition(S703) back to the data-receiving state (S205).

In other words, at predetermined intervals, the receiving node 600announces its presence to surrounding nodes and presents itself as anon-power-saving node.

The signal transmitted in state S702 preferably has the same format asthe ready-to-receive signal S301 transmitted by a power-saving node inFIG. 3.

Alternatively, information indicating whether power-saving handshakingis necessary or not may be added to the ready-to-receive signal S301.

If the receiving node 600 transmits a beacon signal at regularintervals, the information indicating whether power-saving handshakingis necessary may be placed in the beacon signal.

When the transmitting node 400 described in the first embodimentreceives the signal transmitted by the receiving node 600 in state S702,the communication control unit 402 stores information indicating thatthe receiving node 600 is a non-power-saving node in the memory 403.Thereafter, in transmitting data to receiving node 600, transmittingnode 400 will make the transition S502 directly from the decision stateS501 to the data transmitting state S107 as described in the firstembodiment, omitting the power-saving handshaking procedure.

The second embodiment operates in the same way as the first embodiment,except that receiving node 600 periodically transmits information thatit does not require power-saving handshaking, and the communicationcontrol unit 402 in the transmitting node 400 stores this information inits memory 403. The second embodiment therefore provides the sameadvantages as in the first embodiment, with the further advantage ofeasier system set-up and maintenance, because when a new node joins thesystem, the information in its memory and the memories of other nodesdoes not have to be updated by the user.

Like the first embodiment, the second embodiment is applicable tosystems that employ any type of power-saving handshaking protocol,including but not limited to the RICER and TICER protocols described inthe prior art.

The intervals at which non-power-saving receiving node 600 transmits theinformation signal or ready-to-receive signal indicating that it is anon-power-saving node are preferably longer than the intervals at whichthe ready-to-receive signal is transmitted by a power-saving receivingnode. That is, the time-out interval causing transition S701 in FIG. 6is preferably longer than the time-out interval causing transition S202in FIG. 2. This signal is transmitted for the benefit of new nodes thathave recently joined the network, so the signal does not have to betransmitted frequently.

Although separate transmitting and receiving nodes were described in thefirst and second embodiments, the same node may have both transmittingand receiving functions. If the node is a power-saving node, itscommunication control unit may implement the procedures shown in bothFIGS. 2 and 5. If the node is a non-power-saving node, its communicationcontrol unit may implement the procedures shown in both FIGS. 5 and 7.The advantages described in both the first and second embodiments areobtained.

FIG. 8 shows an exemplary information transmission including three nodes400, 600, 650, each having both transmitting and receiving functions.The first node 600 operates continuously; the second node 650 and thirdnode 400 operate intermittently. The communication control unit 601 inthe first node 600 controls transmission as illustrated in FIG. 5, usingdata communication unit 601 and memory 603, and controls reception asillustrated in FIG. 7. The communication control unit 651 in the secondnode 650 controls transmission as illustrated in FIG. 5, using datacommunication unit 651 and memory 653, and controls reception asillustrated in FIG. 2, for example. The communication control unit 401in the third node 400 controls transmission as illustrated in FIG. 5,using data communication unit 401 and memory 403, and controls receptionas illustrated in FIG. 2. Alternatively, the third node 400 may operatecontinuously and its communication control unit 402 may controltransmission as illustrated in FIG. 5 and reception as illustrated inFIG. 7.

Those skilled in the art will recognize that further variations arepossible within the scope of the invention, which is defined in theappended claims.

What is claimed is:
 1. A method of transmitting first information froman information transmitting device to a destination device, comprising:obtaining second information indicating whether or not the destinationdevice requires power-saving handshaking; storing the second informationin a memory in the information transmitting device; selecting at least apower-saving transmission mode and a normal transmission mode accordingto the second information stored in the memory, the power-savingtransmission mode including transmitting and receiving of power-savinghandshaking signals, the normal transmission mode excluding thetransmitting and the receiving of the power-saving handshaking signals;and transmitting the first information in the selected mode, whereintransmitting the first information in the power-saving transmission modecomprises: waiting to receive a predetermined signal; transmitting afirst enabling signal after receiving the predetermined signal; andtransmitting the first information after transmitting the first enablingsignal, wherein the second information is included in the predeterminedsignal.
 2. The method of claim 1, wherein transmitting the firstinformation in the normal transmission mode comprises transmitting thefirst information without waiting to receive the predetermined signaland without transmitting the first enabling signal.
 3. The method ofclaim 1, wherein transmitting the first information in the normaltransmission mode comprises transmitting the first information withoutwaiting to receive the predetermined signal.
 4. The method of claim 1,wherein transmitting the first information in the power-savingtransmission mode further comprises transmitting a second enablingsignal after transmitting the first information, and the secondinformation is also included in a second predetermined signal.
 5. Themethod of claim 4, wherein at least one of the first enabling signal andthe second enabling signal is an acknowledging signal.
 6. A method oftransmitting first information between an information transmittingdevice and a destination device, comprising: obtaining secondinformation indicating whether or not the destination device requirespower-saving handshaking; storing the second information in a memory inthe information transmitting device; selecting at least a power savingtransmission mode and a normal transmission mode according to the secondinformation stored in the memory, the power-saving transmission modeincluding transmitting and receiving of power-saving handshakingsignals, the normal transmission mode excluding the transmitting and thereceiving of the power-saving handshaking signals; and transmitting thefirst information in the selected mode, wherein transmitting the firstinformation in the power-saving transmission mode comprises: waiting toreceive a predetermined signal; transmitting a first enabling signalafter receiving the predetermined signal; transmitting the firstinformation after transmitting the first enabling signal, andtransmitting a second enabling signal after transmitting the firstinformation, wherein the second information is included in thepredetermined signal.